1. Field of the Invention
The invention relates to a process for reading a record carrier as well as to a device applying such a process.
The invention applies especially to the reading of magnetic or optical recordings and, more particularly, to the reading of high-density recordings. It finds a preferential application in recording systems such as computer peripherals and all business systems.
2. Discussion of the Background
In a digital recorder, the decoding of the binary information involves regenerating the time reference signal, referred to as the clock signal, which served in the recording of the information. This clock signal is usually produced by a voltage controlled oscillator (VCO) inserted into a phase locked loop (PLL) which is synchronized with the transitions of the reading signal.
In a multi-track recorder, it is possible to use a single clock signal reconstructed for the tracks as a whole, on condition that the synchronization between all the tracks written on the tape is preserved.
This presupposes that the recording heads and reading heads are aligned, and that the tape does not deform. If these conditions are not strictly complied with, the time references of the various tracks become offset one with respect to another, this being the slippage phenomenon known to those skilled in the art as "skew".
In the case in which the binary information is contained on a large number of parallel tracks, for example in the case in which the pitch between parallel tracks is of the order of 10 to 20 .mu.m, it is virtually impossible to maintain this slippage phenomenon within acceptable limits. It is then known to produce an independent clock regeneration circuit for each track. This has numerous drawbacks including, in particular, that of having to produce a large number of circuits.